Overseas online shopping continues to be a drain on stores in Australia, as Christmas spending gets set to ramp up.

Modelling from the Australian National Retailers Association shows spending is tipped to be $A837 million more than the last seven days.

AAP reports total sales across the country are forecast to hit around $6.6 billion, with shoppers in NSW anticipated to lead the way, spending around $2 billion.

Association chief executive Margy Osmond said surveys show people are likely to spend around 5.4% more this year than during Christmas in 2012.

"I think we are seeing a slight level of improved confidence," Ms Osmond said in Sydney on Sunday.

"Certainly people are feeling reasonably happy about the economy ... we have an election result now and a government in place, all of those things, combined with low interest rates, are making a difference to people's willingness to spend."

While the bulk of spending will be happening at bricks-and-mortar stores, she said domestic retailers will suffer from a shift to overseas-owned websites.

Domestic retailers were disappointed to face another Christmas with no change to GST charges for overseas spending, she said.

"This week alone more than $A1.1 billion is estimated to head offshore to overseas online retailers, with shoppers finalising purchases to ensure gifts are delivered before December 25," she said.

The ANRA expects most women will have finished their Christmas shopping by the end of next week, while men will just be starting.

"This is the week where we really start to see some serious action, but it is usually the week before Christmas where we get the bulk of the spend," she said.